The clinical significance of ischaemic changes on the post-resuscitation electrocardiogram

This editorial refers to Ischemic ECG patterns and its association with survival in OHCA-patients without STEMI: A COACT trials' posthoc subgroup analysis by Eva M Spoormans et al.1 Ischaemic changes such as ST-segment elevation, ST-segment depression, and T-wave abnormalities are a frequent finding on the post-resuscitation electrocardiogram (ECG) in patients with out-of-hospital cardiac arrest (OHCA).2 ST-segment elevation proves to be particularly useful in clinical practice as it is fairly specific for the presence of an acute coronary lesion as the likely cause of the cardiac arrest such that in most cases these patients are directly transferred to immediate coronary angiography.3–5 Interpreting non ST-segment elevation ischaemic changes in the clinical context of OHCA is more challenging. In this issue of European Heart Journal: Acute Cardiovascular Care, Spoormans et al.1 present an analysis of the association of ischaemic changes other than ST-segment elevation (defined by ST-segment depressions of ≥0.1 mV or T-wave inversion in ≥2 contiguous leads) with the severity of myocardial injury, angiographic findings, and mortality. The study is an exploratory post-hoc analysis of the randomized Coronary Angiography after Cardiac Arrest Trial (COACT) trial which compared immediate against delayed/selective coronary angiography in 538 OHCA patients without ST-segment elevation on the post-resuscitation ECG.6 Of the 510 patients analysed in the present analysis, two thirds displayed ST-depression and/or T wave inversion. Patients with ischaemic non ST-segment elevation ECG changes were older and had higher values of troponin T at baseline. Coronary angiography was performed equally often in the ischaemic and non-ischaemic ECG pattern groups. Prevalence and severity of coronary artery disease were higher in patients with compared to without ischaemic ECG patterns including a higher rate of chronic total occlusions. However, there were no significant differences in the rate of acutely unstable lesions or thrombotic occlusions (as angiographic correlates of acute coronary syndrome) between the two groups. Interestingly, about one third of the patients in the ischaemic ECG group undergoing coronary angiography had no significant coronary artery disease at all. Although mortality in the group with ST-depression or T-wave inversion was higher in non-adjusted analysis, ischaemic ECG patterns were not predictive of survival after multivariable adjustment. Survival was instead strongly driven by age and initial time to return of spontaneous circulation (ROSC). The analysis is an important extension to the literature as it is the largest to compare clinical outcome between patients with ischaemic abnormalities (other than ST-segment elevation) and those without such ECG patterns. How could the results translate into clinical practice? First, the value of ischaemic changes other than ST-segment elevation in predicting acute coronary lesions as the trigger of the cardiac arrest is limited. The traditional term, non-specific ST-segment changes’, i.e. not associated with any one condition such as acute coronary syndrome, is therefore also justified in post-cardiac arrest patients. Specifically in the OHCA setting, ischaemia and subsequent ECG changes can result from global myocardial ischaemia as a consequence of low or no blood flow during cardiac arrest. This is especially true for the first minutes after ROSC.7 In consequence, non ST-segment elevation ischaemic changes alone are insufficient to select patients for invasive coronary angiography. It remains to be proven in future analyses if there is a role in conjunction with other parameters (e.g. arrest rhythm, clinical history, troponin values, echocardiographic abnormalities). As both the COACT and TOMAHAWK trials have shown, there is no benefit in performing coronary angiography immediately after hospital admission among haemodynamically stable patients with resuscitated OHCA without ST-segment elevation and a delayed or selective approach is possible and safe for the vast majority.6,8 These results leave ample time for diagnostic measures thereby reducing the likelihood of unnecessary coronary angiographies. In the COACT trial, compared to registries or the TOMAHAWK trial, the number of patients with acute coronary lesions was surprisingly low (at about 15%). Thus, only a minority of patients in this cohort could in theory benefit from (early) coronary angiography. Second, the lack of specificity of ischaemic ECG changes with respect to the prediction of acute coronary lesions does not only reflect a challenge of selection for coronary angiography but also the detrimental situation following prolonged whole-body ischaemia. This so called post-cardiac arrest syndrome includes systemic inflammation following reperfusion, myocardial dysfunction, brain injury, and at worst multi-organ failure.9 Last, the lack of association of ischaemic ECG patterns with survival is not exceptionally surprising as prognosis in OHCA is oftentimes dominated by neurologic injury, thereby minimizing a possible deleterious effect of myocardial ischaemia.10 However, not all OHCA patients experience dismal neurological outcome, and it is likely that there is a subgroup in which myocardial ischaemia and its treatment play an important role in prognosis. It would be worthwhile to assess whether the lack of association of ischaemic non ST-segment elevation ECG patterns with mortality still persists in patients with low neurological risk (e.g. as estimated by the MIRACLE2 score).11 Conflict of interest: None declared.